Printing device with means for conveying paper

ABSTRACT

Printing device with means for conveying paper A printing device ( 10 ) comprises a lower part ( 12 ) and an upper part ( 14 ) that is mounted on said lower part ( 12 ) such that it can pivot about a pivot axis ( 16 ). A print head ( 18 ) and a holding trough. ( 62 ) for a recording medium supply roll ( 64 ) are arranged in the lower part ( 12 ) , and a conveying device ( 24, 30 ) for a recording medium ( 66 ), and a print backing support ( 36 ) spatially associated with the print head ( 18 ) are arranged in the upper part ( 14 ). The upper part ( 14 ) has two side walls ( 42 ) which laterally enclose a recording medium supply roll ( 64 ) put into the holding trough ( 62 ). The invention is characterized in that the print backing support ( 36 ) is planar in the printing area ( 70 ) of the print head ( 18 ), the conveying device comprises a pair of conveyor rollers ( 24 ) that are aligned parallel with the print backing support ( 36 ) and can be driven by a motor, and a tautening device ( 30 ) for the recording medium ( 66 ), and in that the pivot axis ( 16 ) is located underneath the print backing support ( 36 ).

The invention relates to a printing device according to the preamble ofclaim 1.

A printing device of the type mentioned is disclosed by DE 23 09 684 A1.This describes an electrographic printing device having an electrodecomb which extends over the width of the line of print, said devicecomprising a lower part and an upper part mounted on the latter suchthat it can pivot about a pivot axis. The electrode comb and a holderfor a recording medium supply roll are arranged in the lower part, and aconveying device, designed as a printing roller, for a recording mediumis arranged in the upper part. The electrode comb is associatedspatially with the printing roller, the individual electrodes beingsprung against the printing roller. The printing roller therefore formsa print backing support and, in interaction with the electrodes, arecording medium conveying device. The upper part has two side wallswhich laterally enclose a recording medium supply roll put into theholder.

The known arrangement has the advantage that a recording medium supplyroll can be put in particularly simply. The arrangement may also behighly suitable for a printing device which, as a print head, has anelectrode comb which touches the recording medium only at a line.However, if a print head is to be used which opposes the recordingmedium flatly and at a distance, then this arrangement cannot be used.

WO 91 13765 A1 describes a printer which likewise comprises a lower partand an upper part that is mounted on the latter such that it can pivotabout a pivot axis. A print head is arranged in the lower part, and aprinting bar and a holder for a recording medium supply roll arearranged in the upper part. Provided as a conveying device for arecording medium are two pairs of conveyor rollers of which one, asviewed in the conveying direction of the recording medium, is locatedupstream of the printing bar and is driven at the same time as a secondpair of conveying rollers, which are arranged downstream of the printingbar. It is seen as a drawback that, because of the arrangement of therecording medium supply roll in the upper part, the recording medium hasto be led through a slot and around the upper conveying roller locatedupstream of the printing bar and also around the printing bar itself.Replacing a recording medium supply roll is therefore difficult andtime-consuming.

It is therefore an object of the invention to develop a printing deviceof the type mentioned to the effect that a print head can be used whichopposes the recording medium at a distance and whose printing elementsextend at least over the width of a line of print.

For a printing device according to the preamble of claim 1, the objectis achieved by the defining features of claim 1.

According to the invention, the print backing support is planar in theprinting area of a serial-character or serial-column print head that canbe displaced in the direction of a line of print, the conveying devicecomprises a pair of conveyor rollers that are aligned parallel to theprinting area and can be driven by a motor, and a tautening device forthe recording medium and, as viewed in the direction of a line of print,a parking area for the print head is arranged beside the printing area.

The planar configuration of the print backing support ensures that thedistance to the recording medium is the same for all printing elements.The print backing support can be designed as a simple supporting platein the case of the print head which operates without contact but, whenan impact print head is used, must be designed as a printing bar. Acombination, described further below, of a pair of conveyor rollersarranged on one side of the print backing support and a tautening devicearranged on the other side ensures that the recording medium is alwaystautly tensioned in the area of the print backing support.

The print head is preferably an ink jet print head which can be movedparallel to the print backing support in the direction of a line ofprint and which can print one or else a number of lines of printsimultaneously.

According to a development of the invention, good tensioning of therecording medium in the area of the print backing support is achieved bya pair of conveyor rollers, as viewed in the conveying direction of therecording medium, being arranged downstream of the print backingsupport, and a recording medium brake formed of a material with a highcoefficient of friction being arranged upstream of the print backingsupport. In this case, the first pair of conveyor rollers pulls therecording medium held back by the recording medium brake past the printbacking support. Here, the recording medium brake can consist of anelastically compressible plastic strip with a high coefficient offriction, which is supported on the print backing support.

According to an alternative development of the invention, the tensioningof the recording medium in the area of the print backing support isachieved by a first pair of conveyor rollers, as viewed in the conveyingdirection of the recording medium, being arranged upstream of the printbacking support, and a second pair of conveying rollers, driven at thesame time as the first pair of conveyor rollers, being arrangeddownstream of the print backing support, the second pair of conveyorrollers being driven at a slightly higher circumferential speed than thefirst pair of conveyor rollers and having a coefficient of frictionwhich is slightly lower than said first pair, so that the recordingmedium advance step is determined by the first pair of conveyor rollers.

According to a preferred embodiment of the subject of the invention, thepair of conveyor rollers or else the first and second pairs of conveyorrollers are formed by a driven roller which is mounted in the upper partand acts on the rear of the recording medium, and a backing roller whichis mounted in the lower part, is acted on with the force of a spring inthe direction of the driven roller, acts on the recording side of therecording medium and runs freely. The fact that the driven rollers acton the rear of the recording medium means that smearing of the stillfresh imprint is avoided. The backing rollers are carried along by therecording medium as it is advanced, that is to say moved together withthe latter without slip. This reliably avoids smearing of the imprint.

The arrangement of the pivot axis of the upper part at the same heightas a center line passing through the first backing roller and the firstdriven roller, or underneath said line, ensures that when the upper partis pivoted into its open position, the pair of conveyor rollers and thetautening device are already open after sweeping over a minimum pivotingangle, that is to say the recording medium is not carried along with itas it is pivoted.

According to a preferred embodiment of the invention, at least onelatching lever provided with a claw is pivotably mounted on the lowerpart, and a locking pin is arranged on that side wall of the upper partwhich is adjacent to the latching lever. Of course, the conversearrangement is also possible. The important factor is that the twolocking elements are designed to be complementary to each other.

According to an advantageous development of the subject of theinvention, a two-armed unlocking lever is pivotably mounted on the sidewall adjacent to the latching lever, on the side of the upper part thatis remote from the pivot axis, one arm of said unlocking lever beingintended to engage on the at least one latching lever with the effect ofunlocking the complementary locking elements.

It is particularly advantageous if the at least one latching lever canbe moved into the unlocking position only when the print head is in theparking area or an acceleration area that is located in front of theprinting area, that is to say outside the printing area. As a result,during the replacement of the recording medium supply roll, thesensitive mouthpiece of the print head is protected against unauthorizedcontact, and the hands of the operating staff are protected againstsoiling.

In order to make manual displacement of the print head impossible whenthe printer is switched off, the print head is additionally blocked inthe parking area or the acceleration area if the upper part is locatedoutside the printing position.

In order to reduce still further the risk of smearing the still freshink, according to a preferred development of the invention, the backingrunning roller that is located downstream of the print head in theconveying direction, that is to say at least the backing roller of thepair of conveyor rollers or of the second pair of conveyor rollers, hasa surface structure which cannot be wetted by printing ink and/orconsists of a material which cannot be wetted by printing ink.

Further features and advantages of the invention emerge from thefollowing description of an exemplary embodiment, which will beexplained by using the appended drawing, in which:

FIG. 1 shows a schematic side view of a printing device with the upperpart closed,

FIG. 2 shows a schematic side view of the printing device with the upperpart folded up,

FIG. 3 shows the printing device in a schematic plan view.

In FIG. 1, a printing device is designated generally by 10. It comprisesa lower part 12 with side cheeks 13 and an upper part 14. The latter isheld such that it can be pivoted about a pivot axis 16 in the rear areaof the lower part 12, as the arrow A shows.

An ink jet print head 18 is mounted on the lower part 12 such that itcan be displaced at right angles to the plane of the drawing on guiderails 19 which are held in the side cheeks 13. Arranged underneath theink jet print head 18 is a first backing roller 22, which can rotatefreely on a first shaft 20, belonging to a first pair of conveyorrollers 24, and arranged above the ink jet print head 18 is a secondbacking roller 28, which can rotate freely on a second shaft 26,belonging to a second pair of conveyor rollers 30. The two ends of theshafts 20, 26, which extend parallel to the displacement direction ofthe ink jet print head 18, are resiliently prestressed in the directionof the upper part 14 by a compression spring 32 and 34, respectively(only one compression spring can be seen in each case).

Fixed to the upper part 14, opposite the ink jet print head 18, is aprint backing support 36 which is planar in the area of the ink jetprint head 18. Arranged underneath the print backing support 36 is afirst driven roller 38 of the first pair of conveyor rollers 24, andarranged above the ink jet print head 18 is a second driven roller 40 ofthe second pair of conveyor rollers 30. The first and the second drivenroller 38, 40 are driven by a drive motor which is common to both,arranged in the lower part 12 but not illustrated. The second drivenroller 40 has a slightly greater circumference than the first drivenroller 38. The print backing support 36 and the first and the seconddriven roller 38, 40 are held in two side walls 42 that are alignedparallel to each other, the print backing support 36 projecting slightlybeyond the driven rollers 38, 40 in the direction of the print head 18,in order that a recording medium 66 rests fully on said print backingsupport 36. The pivot axis 16 of the upper part 14 is located at thesame height as a center line 25 that passes through the first backingroller 22 and the first driven roller 38. It can also be locatedunderneath said line. This means that when the upper part 14 is pivotedinto its open position, the first pair of conveyor rollers 24 and thetautening device—the second pair of conveyor rollers 30 in the exemplaryembodiment illustrated—are already open after sweeping over a minimumpivoting angle in the direction of the arrow A, that is to say therecording medium 66 is not carried along as the upper part 14 ispivoted. Conversely, when pivoting the upper part 14 back into itsprinting position, the recording medium 66 is first of all clamped inthe first pair of conveyor rollers 24. If the recording medium 66 istautened manually during the further pivoting of the upper part 14 intothe printing position, then the tension is maintained when the secondpair of conveyor rollers 30 also clamps the recording medium 66 in.

From each side wall 42, a locking pin 44 protrudes perpendicularlyoutward. In the position of the upper part 14 that is shown in FIG. 1,the locking pin 44 engages in a claw 46, which is incorporated into oneflank of a latching lever 50 that can be pivoted about a pivot pin 48.Above the claw 46, the latching lever 50 tapers to form an insertionbevel 52 for the locking pin 44. The latching lever 50 is acted on inthe direction of its locking position, illustrated by continuous lines,with the force of a locking spring 54.

On the side walls 42 of the upper part 14, in each case a two-armedunlocking lever 56 is mounted such that it can be pivoted about a secondpivot axis 57 that passes perpendicularly through the side walls 42.

The upwardly projecting arms of the unlocking levers 56 are connected toeach other by a handle 58, so that the unlocking lever arrangement 56,58 embraces the upper part 14 in a U shape. The free arm 60 of eachlocking lever 56, in its rest position illustrated by continuous lines,rests on the flank of the latching lever 50, into which the claw 46 isalso incorporated.

Arranged in the lower part 12 of the printer 10, between the side walls42 of the upper part 14 and close to the pivot axis 16, is an upwardlyopen holding trough 62 for a recording medium supply roll 64. The end ofthe recording medium 66 running away from the underside of the recordingmedium supply roll 64 is led from below around the first and the secondpair of conveyor rollers 24, 30.

By adjusting the unlocking levers 56 into their unlocking position 56′,illustrated by dash-dotted lines, their free arms 60 press the latchinglevers 50 into their unlocking position 50′, illustrated by dash-dottedlines, so that the upper part 14 can be pivoted into its folded-upposition illustrated in FIG. 2. In the process, the free arms 60 of theunlocking levers 56 come out of engagement with the latching levers 50which, under the force of the locking springs 54, return to theiroriginal position. In the folded-up position of the upper part 14, therecording medium supply roll 64 can be put into the holding trough 62,and the recording medium 66 can be placed on the driven rollers 38, 40.

If the upper part 14 is moved into its folded-down position, shown inFIG. 1, then the locking pins 44 slide along on the insertion bevels 52until they latch into the claws 46. In the process, the recording medium66 is clamped into the pairs of conveyor rollers 24, 30. If their drivemotor is briefly energized, the recording medium 66 is additionallytautened upstream of the print backing support 36, and the printer 10 isready to print.

It can be gathered from the plan view in FIG. 3 that the area betweenthe side cheeks 13 is divided up into three sections: an accelerationarea 68, a printing area 70 and a parking area 72. The print backingsupport 36 extends over the entire printing area 70. In the parkingarea, which adjoins the printing area 70 on the right in FIG. 3, thereis arranged a docking station 74, as it is called, which comprises acovering cap 76 that prevents the ink jet print head 18 drying out, anda wiping lip 78. The docking station 74 can also additionally comprise asuction device for cleaning the ink nozzles of the ink jet print head18. Docking stations for ink jet printers are generally known. Aspecific description of their construction and their mode of action istherefore superfluous. The acceleration area 68 is needed if printing isto be carried out in both conveying directions of the ink jet print head18 and, at the same time, with a constant print quality. When the inkjet print head 18 starts from the side cheek 13 on the left in FIG. 3,it has already reached its intended speed when it enters the printingarea 70.

Within the parking area 72, a first arm 80 of a blocking lever 82 thatis acted on in the direction of the upper part 14 by the force of athird compression spring 86 projects into the displacement path of theink jet print head 18. A second arm 84 of the blocking lever 82 engagesbehind the latching lever 50 (on the right in the figure) , so that thelatter is blocked and the upper part 14 cannot be pivoted out of itsprinting position. The blocking position of the blocking lever 82 isillustrated. dash-dotted. If, however, the ink jet print head 18 ismoved into its parking position, illustrated in FIG. 3, it displaces theblocking lever 82 to the right into its release position, illustrated bycontinuous lines, the right-hand latching lever 50 is released and theupper part 14 can be pivoted out of the printing position.

In addition, a print head blocking lever 88 is mounted such that it canbe displaced vertically in the lower part 12 of the printer 10. Said,lever has a first arm 90 which projects into the displacement path ofthe ink jet print head 18. A second arm 92 of the print head blockinglever 88 projects into the pivoting path of the upper part 14. The printhead blocking lever 88 can be displaced between a blocking position,with its first arm 90 projecting into the displacement path of the inkjet print head 18 (illustrated dash-dotted in FIG. 1) and a positionwhich clears the displacement path (illustrated, by continuous lines inFIG. 1). It is prestressed in the direction of its blocking position bythe force of a fourth compression spring 94. The print head blockinglever 88 is arranged with respect to the displacement path of the inkjet print head 18 such that the latter can be held firmly in the parkingposition. As long as the upper part 14 is in its printing position, theprint head blocking lever 88 is held in its release position, and theink jet print head 18 can be displaced as desired. If the upper part 14is pivoted out of the printing position, the print head blocking lever88 is displaced into its blocking position, driven by the fourthcompression spring 94.

The blocking lever 82 and the print head blocking lever 88 act togetherin such a way that, firstly, the upper part 14 can be moved out of itsprinting position only when the ink jet print head 18 is located in theparking area 72, and that, secondly, the ink jet print head 18 can bemoved out of the parking area 72 only when the upper part 14 is locatedin its printing position. As a result, reliable protection for the inkjet print head 18 against accidental contact is achieved.

What is claimed is:
 1. A printing device (10) comprising a lower part(12) and an upper part (14) that is attached to said lower part (12), animaging device (18) and a holding trough (62) for a recording mediumsupply roll (64) being arranged in the lower part (12), and a conveyingdevice for a recording medium (66), and a print backing support (36)extending over a printing area (70) and spatially associated with theimaging device (18) being arranged in the upper part (14), the upperpart (14) having two side walls (42) which laterally enclose a recordingmedium supply roll (64) put into the holding trough (62), and the upperpart (14) being capable of pivoting about a pivot axis (16), between anopening position that opens the holding trough (62) and a printingposition, in which the print backing support (36) is opposite theimaging device (18), characterized in that the imaging device is aserial-character or serial-column print head (18) which can be displacedin the direction of a line of print, the print backing support (36) isplanar in the printing area (70) of the print head (18), the conveyingdevice comprises a first pair of conveyor rollers (24) that are alignedparallel to the printing area (70) and can be driven by a motor, thefirst pair of conveyor rollers (24), as viewed in the conveyingdirection of the recording medium (66), being arranged upstream of theprint backing support (36), and a tautening device for the recordingmedium (66), the tautening device comprising a second pair of conveyorrollers (30) driven at the same time as the first pair of conveyorrollers (24) arranged downstream of the print backing support (36), thesecond pair of conveyor rollers (30) being driven at a slightly greaterconveying speed than the first pair of conveyor rollers (24) and havinga coefficient of friction that is lower than the first pair of conveyingrollers (24), and in that, as viewed in the direction of a line ofprint, a parking area (72) for the print head is arranged beside theprinting area (70).
 2. The printing device as claimed in claim 1,characterized in that the print head (18) can print a number of lines ofprint simultaneously.
 3. The printing device as claimed in claim 1,characterized in that the print head is an ink jet print head (18). 4.The printing device as claimed in claim 1, characterized in that thepivot axis (16) is located at the same height as a center line (25)which passes through the first backing roller (22) and the first drivenroller (38), or underneath said line.
 5. The printing device as claimedclaim 1, characterized in that at least one latching lever (50) ispivotably mounted on the lower part (12) and, on the side wall (42) ofthe upper part (14) adjacent to the latching lever (50), there isarranged a first locking element designed as a locking pin (44) or as aclaw and, on the latching lever (50), there is arranged a second lockingelement (46) which is designed to be complementary the first lockingelement.
 6. The printing device as claimed in claim 5, characterized inthat on the side wall (42) that is adjacent to the latching lever (50),on that side of the upper part (14) that is remote from the pivot axis(16), a two-armed unlocking lever (56) is pivotably mounted, whose onearm (60) is intended to engage on the at least one latching lever (50)with the effect of unlocking the complementary locking elements (44,46).
 7. The printing device as claimed in claim 6, characterized in thata latching lever (50) is arranged on both sides of the lower part (12),and an unlocking lever (56) is arranged on both sides of the upper part(14), in that the unlocking levers (56) are connected to each other in aU shape, and in that the U-shaped unlocking lever arrangement (56, 58,56) engages over the upper part (14) and can be pivoted about a pivotaxis (57) which passes perpendicularly through the side walls (42) ofthe upper part (14).
 8. The printing device as claimed in claim 5,characterized in that the at least one latching lever (50) can be movedinto the unlocking position only when the print head (18) is located inthe parking area (72) or the acceleration area (68).
 9. The printingdevice as claimed in claim 8, characterized in that the print head (18)is blocked in the parking area (72) or the acceleration area (68) if theupper part (14) is outside the printing position.
 10. The printingdevice as claimed in claim 1, characterized in that, at least on oneside of the printing area (70), an acceleration area (68) for the printhead (18) adjoins said printing area (70).
 11. The printing device asclaimed in claim 1, characterized in that at least the backing roller(28) of the first pair of conveyor rollers (24) or of the second pair ofconveyor rollers (30) has a surface structure that cannot be wetted byprinting ink and/or consists of a material that cannot be wetted byprinting ink.
 12. A printing device (10) comprising a lower part (12)and an upper part (14) that is attached to said lower part (12), animaging device (18) and a holding trough (62) for a recording mediumsupply roll (64) being arranged in the lower part (12), and a conveyingdevice for a recording medium (66), and a print backing support (36)extending over a printing area (70) and spatially associated with theimaging device. (18) being arranged in the upper part (14), the upperpart (14) having two side walls (42) which laterally enclose a recordingmedium supply roll (64) put into the holding trough (62), and the upperpart (14) being capable of pivoting about a pivot axis (16), between anopening position that opens the holding trough (62) and a printingposition, in which the print backing support (36) is opposite theimaging device (18), characterized in that the imaging device is aserial-character or serial-column print head (18) which can be displacedin the direction of a line of print, the print backing support (36) isplanar in the printing area (70) of the print head (18), the conveyingdevice comprises a first pair of conveyor rollers (24) that, are alignedparallel to the printing area (70) and can be driven by a motor, thefirst pair of conveyor rollers (24), as viewed in the conveyingdirection of the recording medium (66), being arranged upstream of theprint backing support (36), and a tautening device for the recordingmedium (66), the tautening device comprising a second pair of conveyorrollers (30) driven at the same time as the first pair of conveyorrollers (24) arranged downstream of the print backing support (36), thesecond pair of conveyor rollers (30) being driven at a slightly greaterconveying speed than the first pair of conveyor rollers (24) and havinga coefficient of friction that is lower than the first pair of conveyingrollers (24), and in that, as viewed in the direction of a line ofprint, a parking area (72) for the print head is arranged beside theprinting area (70), the first pair of conveyor rollers (24) or else thefirst pair of conveyor rollers (24) and the tautening device beingformed by a driven roller (38; 40) which is mounted on the upper part(14) and acts on the rear of the recording medium (66), and a backingroller (22; 28) which is mounted on the lower part (12), being acted onin the direction of the driven roller (38; 40) by the force of a spring(32; 34), acts on the recording side of the recording medium (66) andruns freely.